Common ailments of horses are diseases such as the growth of an infection around the hoof. The infection can be a bacteria or a fungus. The horse hoof is the structure surrounding the distal phalanx of each of the four limbs of Equus species, which is covered by complex soft tissue and keratinised structures. Since a single digit must bear the full proportion of the animal's weight that is borne by that limb, the hoof is of vital importance to the horse. The health and the strength of the hoof is crucial for horse soundness.
The hoof is made up by an outer part, the hoof capsule and an inner, living part, containing soft tissues and bone. The cornified material of the hoof capsule covers, protects and supports the foot bone and specialised soft tissues including: tendons, ligaments, fibro-fatty and/or fibrocartilaginous tissues and cartilage. The walls originate from the coronet band. Walls are longer in the anterior portion of the hoof, intermediate in length in the lateral portion and very short in posterior heel portion. Heels are separated by an elastic, resilient structure named the ‘frog’.
The bottom of the hoof includes the wall's free margin that encircles most of the hoof and the triangular frog. Lateral to the frog are two grooves, deeper in their posterior portion, named ‘collateral grooves’. At the heels, the posterior portion of the walls bend inwards sharply, following the external surface of collateral grooves. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating keratinised material, called the ‘sole’.
The walls cover and protect the sensitive internal hoof tissues and dissipating the contact energy and to provide grip on different terrains. The walls have a thickness of approximately 6 mm-12 mm. The walls are composed of distinct layers: the pigmented layer and the water line, which is also known as the white line, that merge in a single mass. Horseshoes are fixed to the walls by driving nails oblique to the walls. The nails enter the wall at the outside edge of the white line and they emerge at the wall's surface, approximately 15-20 mm from the base of the wall.
The frog is a triangular structure that extends forward across about two-thirds of the sole. Its thickness grows from the front to the back and, at the back, it merges with the heel periople. The frog has a rubbery consistency and functions as shock absorbers and improves the hoof's grip on hard, smooth ground. In the free-roaming horse, the frog hardens into a callous consistency with a near-smooth surface. In contrast, the frog of a stabled horse can degrade with bacterial and fungal activity into an irregular, soft, slashed surface.
There are various diseases that can infect a hoof. Thrush is a fungal disease which damages the frog and leaving open sores which eventually create significant pain and tenderness to the animal. The thrush may result in crippling of the horse if the condition is not treated. The frog and sole of the hoof can also be attacked by bacterial infections. Many treatments have been developed over the years. These treatments typically require anti-fungal and/or anti-bacterial chemicals and can be fairly difficult to apply to the hoof.